Pressure sensitive hectograph transfer element



Sept. 11, 1956 PRESSURE SENSITIVE HECTOGRAPH TRANSFER ELEMENT FiledMarch so, 1949 lmaentor DaiyZas f1. New/77am (lttomegs A. NEWMAN2,762,715

United States Patent 2,762,715 PRESSURE SENSITIVE HECTOGRAPH TRANSFERELEMENT Douglas A. Newman, Glen Cove, N. Y., assignor to Columbia Ribbonand Carbon Manufacturing Company, Inc., Glen 'Cove, N. Y., a corporationof New York Application March 30, 1949, Serial No. 84,410 2 Claims. (Cl.117-36) This invention relates to transfer elements for manifolding andduplicating use and particularly to transfer elements having transferlayers containing soluble dyes such as crystal violet, methyl violet,brilliant green, magenta and the like. Dyes of this character aresoluble to some extent in waxes, fatty acids, fatty alcohols used incompounding transfer materials, and are also highly soluble in alcoholand water. When a portion of the transfer layer has been deposited on areceiver or master, usually by pressure, to form an image, the latter iscapable of being moistened with a suitable solvent such as alcohol orwater, whereby copy sheets which are brought into contact with theimage-bearing master receive a portion of the dye in the shape of theimage, and a plurality of copies can be obtained in this fashion. Thisprocess is commonly referred to as hectographic duplication and thetransfer element as hectograph carbon.

One of the most severe drawbacks ordinarily encountered in the use of ahectographic duplication process is the difliculty of handling thehectograph carbon sheets without contaminating the operators hands andclothing with coloring matter, and without producing smudges on themaster either directly from the carbon, or by way of the operatorshands. One main reason for this is that the available dye materialswhich have sufiiciently strong coloring power to provide a plurality ofcopies, are water soluble and thus migrate readily under the influenceof the moisture usually present on the operators hands. Therefore, underordinary circumstances, the nuisance occasioned by soiled hands as wellas the danger of damaged clothing and spoiled copies is an importantfactor to be reckoned with.

Various methods are used to attack this problem, one of which has been,particularly where hectograph carbon is concerned, the manufacture ofmaster units, or units consisting of a folded sheet, one-half of whichcarries the transfer coating, and the other half of which forms adetachable master sheet. This is done in order to avoid such smudging asmay be due to unnecessary handling of the hectograph carbon during thetyping or inscribing operation. While the handling is in fact minimizedin this fashion, additional problems are introduced which make themaster unit construction by itself somewhat less than a complete answerto the problem. It is found, for example, that interleaved protectivesheets are required to prevent smudging of the master sheet surface bythe adjacent transfer layer. The use of these interleaved sheets entailsmany handlings of the same at every stage in the process which is initself undesirable. Furthermore, during any period when the interleavingsheet must be removed, for example during the preprinting of forms, alittle of the dye material of the transfer coat migrates to the mastersheet in response to moisture or chemicals found in the master sheetpaper, or by attrition in response to the frictional contacttherebetween; or certain oils commonly used in compounding the transfermaterial, are attracted to the surface of the master sheet and so afiectthe same that its suitability for use in the hectograph process isimpaired.

Other attempts have been made to correct this condition, or at least tomoderate its effects by providing a transfer sheet which has aprotective coating of some sort over the transfer layer in order tominimize both the direct mechanical smudging of the surface of thetransfer sheet and contamination of the operators hands due to moistureinspired dye migration. While these have been successful to a degree, inmany cases the coating is such as to impair the color-releasing propertyof the transfer sheet to an undesirable degree, with the result that thepurchaser often prefers to dispense with the protective coating and relyprimarily on the care and patience of the operator in order to achieveclean masters capable at the same time of producing a full quota ofcopies.

It is an object of the invention, therefore, to provide a transfersheet, especially for hectographic use, which is adequately protectedagainst smudging, but which at the same time is capable of releasing itscolor during the transfer operation in such a way that the number orquality of copies obtainable from a master sheet will not be adverselyaffected.

One manner in which the color-releasing power of the transfer layer isoften seriously affected by the presence of a protective overcoat hasbeen discovered to be the partial commingling of the overcoatingmaterial with the material of the transfer layer at the interface. Thisaction appears to result either from the dilution of the outer mostportion of the transfer layer by the overcoating material, during itsliquid stage while undergoing application, or the migration of the dyematerial from the outer portion of the transfer layer into the underportion of the overcoating layer by reason of the solvents used, or theinherent partial solvent characteristic of the material of theovercoating layer for the dye material of the transfer layer. Thisphenomenon occurs particularly when the overcoating material usedincludes a solvent which is a solvent for the dye of the transfer coat,or has a fusion temperature similar to or higher than the binder of thetransfer coat. It appears that the effect is to form a relatively thickzone of low color concentration at a critical place in the combinedcoating so located that when transfer occurs the material of this zoneis uncovered for use and becomes the working surface of the masterimage, whereby copies of unacceptably low color intensity result.Another object of the invention, therefore, is the production of atransfer sheet which can be made without the occurrence of such a lowcolor intensity zone to any serious degree, and the devising ofpracticable methods for making the same.

In the past various materials have been used as the basis for protectiveovercoating layers, but waxes or coating compositions consisting for themost part of waxy material have proved particularly practical fromseveral standpoints. For one thing, when a sufiicient proportion of waxis used, the overcoating has the most desirable relationship as regardsthe combined qualities of adhesiveness to the surface of the mastersheet, and a degree of frangibility which allows the image to come offreadily and with a clean outline. Such a coating furthermore lacks thetendency to provide the barrier against transfer which is noticed withcoatings consisting mainly of other materials, provides a consistencyand texture which is most readily accommodated by the usual carbon papercoating,

handling and surfacing equipment, and is generally more satisfactoryexcept for its unfortunate dilution or commingling tendencies i r 1relation to the usual wax-base transfer layer. The invention, therefore,has for another.

object the provision of a transfer sheet employing a protective overcoatconsisting of layers essentially of waxy material, but whereincommingling between the transfer layer and the overcoating material islargely inhibited, whereby the beneficial characteristics of a wax coatare taken advantage of, and its drawbacks avoided.

Still another object of this invention is the production of transfersheets embodying the foregoing improvements in combination with the usein a protective coating of a shielding component of the type consistingof lamelliform particles suspended in the coating composition. Thisparticular feature is disclosed in detail and claimed in my copendingapplication Serial No. 59,120, filed November 9, 1948, now Patent No.2,729,575.

The invention further includes the arrangements of the features andsteps outlined above in various combinations particularly suited to anyspecial use for which the transfer sheet is intended, or to theexigencies of its manufacture.

Additional features and advantages will hereinafter appear.

In the drawing:

Figure l is a fragmentary sectional view of a transfer sheet made inaccordance with practices followed in the prior art.

Fig. 2 is a fragmentary section of a transfer sheet which has aprotective coating in accordance with the present invention.

Fig. 3 is a perspective view of a master unit structure embodying one ormore of the improved features and elements illustrated in Fig. 2.

The condition ordinarily achieved when a transfer sheet, such ashectograph carbon, is sought to be protected by an overcoat according tocertain known procedures, is illustrated in Pig. 1. in this figure afoundation sheet 10 has had a coating of wax-base transfer material 11applied thereto. Thereafter a coating 12 usually of wax is applied,normally by reducing the material to molten condition, spreading it onthe surface of the transfer layer, and then cooling the same. The line Aindicates the approximate level of the transfer layer 11 beforeapplication of the coating 12, and the position at which the interfacebetween the coatings would be expected to occur. However, it is foundthat the material of coating 12, due to its temperature, softens thecoating 11 and mixes therewith as shown in Fig. l with the result thatthe color concentration in the coating 11 is seriously reduced as fardown as the position indicated approximately by the line B, the colorbeing dispersed substantially an equal distance above the line A in thecoating 12. The effect of this condition is apparent when it isconsidered that the transfer layer will be largely removed to the mastersheet in the locality where inscribing pressure is applied, and invertedthereon with the surface C, which is here shown as contiguous to thefoundation 10, exposed for use. It can be seen that the image thusformed consists of a thin initial layer of a thickness B-C which is ofsubstantially full color concentration and capable of operating in anacceptable fashion, backed up by a layer equal to about twice thethickness AB in which the color strength is severely diluted. Thiscondition is particularly serious where the transfer sheet is being usedin the hectographic reproduction process and intense coloring power isrequired of the master image in order that a substantial number ofcopies may be made therefrom, for all but the first thin layer B-C willbe of inferior if not unacceptable color intensity thus seriouslyreducing the number of usable copies that can be taken from the imageand thus limiting its useful life to a small part of the normal life ofsuch an image.

This invention has been made to prevent the condition illustrated inFig. l, and one means for accomplishing this result is shown in Fig. 2which illustrates an arrangement by which commingling of the coatings atthe interface between the transfer coat and the protective overcoat isavoided.

Here the transfer coating of usual composition is designated by thecharacter 41. To the surface of this coating is applied a barrier layer43 having a film forming constituent which is rendered liquid bydissolving the same i in a suitable volatile solvent, This solution ispreferably applied to the transfer layer by spreading in the usualmanner and by the ordinary equipment employed in carbon coatingmachines. For this reason, it is important that the solvent used be onewhich is ineffective against any soluble dye which may be used in thetransfer layer 41. Since these dyes are normally primarily water andalcohol soluble dyes such as crystal violet and methyl violci ethyleneare examples of suitable solvents for this purpose. One form of thebarrier coat 43 may include mainly wax or waxy material, and a certainamount of a synthetic resin, for example chlorinated rubber, as atoughening ingredient. it has also been discovered that a coatingmaterial of this character takes on unusual covering power and may beformed with a minimum thickness when a shielding component oflamelliform particles 44 such as powdered aluminum, bronze, or graphite,or ground mica or fish scales is included. The importance of such aningredient and the manner of its operation is set out at length in mysaid copending application. One example of a solution which suggests ingeneral the proportions suitable for casting this layer is as follows:

Ingredients: Parts by weight Tornesit (chlorinated rubber-Hercules) 1%Beeswax 2% Carbon tetrachloride 70 When a shielding component isdesired, one part by weight of the ingredient, for example aluminumpowder may be added to the foregoing formula.

While it has previously been attempted to use a single protective filmembodying a proportion of synthetic resin as a smudge preventer fortransfer sheets, this has been largely unsuccessful due to its failureto release the color properly when transfer is attempted when applied ina layer thick enough to be considered operative from the standpoint ofprotection. Here, however, the coating is so composed that its mainconstituent is wax and the thickness is reduced so that this coating isof itself only a partial smudge protector being not over .0001 inch inthickness. The reduced thickness is also important for the reason thatthe coating is most easily applied by spreading the same in dissolvedcondition. While the solvents used are not such as to have a liberatingeffect on the dye material of the transfer layer, a slight comminglingeffect between the waxy constituents of layers 41 and 43 may possiblyoccur. By holding the layer 43 to a nominal thickness, the activesolvent present per unit area of the transfer layer 41 is minimized,whereby penetration of the dilution effects of the solvent applied layer43 upon the transfer layer 41, if they occur, extend to a depth which ispurely nominal and in no way detrimental to the working surface of theimage when pressure inspired separation at approximately the level Btakes place. Once the solvent barrier layer 43 is in place and hardenedby evaporation of the solvents, its character as a barrier may befurther improved, if desired, by polishing the surface as by contactwith a buffing wheel. This tends to dispose the surface particles of theflaky or lamelliform ingredient, when used, more nearly parallel to thefoundation sheet with the result that the protective power of thecoating -'13 is further enhanced. Thereafter, a coat 42 of waxy materialmay be spread in any desired manner, and preferably by the convenientand usual method of melting the composition and applying the moltenmaterial directly to the surface of layer 43 in an extremely thincoating, of not more than .0002 inch in thickness. However, while theprotective layer 42 is conveniently and inexpensively placed by meltingand spreading, this results in no commingling of the wax with thetransfer layer 41, for the hardened barrier coat 43 which intervenesprovides an insulating layer, and it is found that the period of timerequired to apply, spread and cool the vzrbon. tetrachloride, solventnaphtha and trichlor melted mixture is short enough that the softeningeffect will not be able to penetrate the barrier layer 43 when ordinaryequipment and procedures are employed.

Although the reasons for the extremely beneficial results obtained whenthe transfer sheet is constructed as described in connection with Fig. 2are not "entirely understood, it appears that the waxy layer 42 actssomewhat as a primary armor for turning aside normal frictlon andabrasive attacks and combines with the armor formed by the surface ofbarrier layer 43 to prevent mechanical smudging as well as inhibitingany effects in the nature of migration of the dye or oils of thedye-bearing layer dueto moisture or the proximity of any oil-receptivesurface. It appears that the protective effect may be due in part to thepresence of distinct surfaces 1n the overcoat, in which case thepresence of a plurality of layers with well-defined interfaces betweenthem is probably responsible at least in part for the protectiveeffectiveness of the structure described. On the other hand, theadhesiveness of layer 42 for both the layer 43 and for the surface ofthe paper to which the image is applied is very high under the values ofpressure normally used in transfer so that the color released to theimage is found to be a substantial improvement over that which isreleased when a single, thick coating made substantially in accordancewith the disclosure pertaining to coating, 43, is used. In fact thecolor release value for the combination disclosed above is equal to oreven greater than that for the usual transfer layer alone in the absenceof any protective film. This procedure is so effective, in fact, that athoroughly practical protection can be achieved, even without benefit ofthe particles 44, when the combined thickness of the coatings 43 and 42does not exceed .0002 inch. The fact that a useful protective coveringof such restricted dimensions can be cast, is in itself a substantialcontribution to the power of the sheet to release its color underpressure. Another aspect of the thickness of the protective coat isexpressed by the statement that with average materials and papers ofordinary character, clear transfer of an image can not be expected whenthe combined thickness of the layers on the transfer sheet exceeds acertain determinable value which, using coating materials and papersordinarily employed, is approximately .0011 inch. This relationship isone which can be readily determined empirically and its significancelies in the fact that the thinner a protective coating can be made andstill operate effectively, the more room that remains for color bearingor transfer material.

Fig. 3 represents the invention embodied in the form of a master unit60. This unit comprises a paper sheet folded to form the portions 61 and64. The former serves as a detachable master while the latter acts asthe transfer element. The unit 60, due to the connection of the parts atfold 67, can be placed in a typewriter, or otherwise prepared forinscription without unnecessary handling of the transfer sheet.

The portion 64 has on its inner surface a deposit 65 of transfermaterial which has been protected by the method described above. Theprotection thus afforded is sufficient to prevent smudging of the innersurface 63 of the master sheet, or the migration of coloring matter oroils thereto which would impair its operation as a master. The usualinterleaving normally employed with such units is consequentlyunnecessary. As a result, inscription by printing, writing or typing onthe surface 62 to form a reverse reading image on the master surface 63,or on surface 66 when a direct reading image on surface 63 is desired,may proceed directly without the necessity for removing and replacingany separating sheet.

It will be seen, therefore, that this invention provides a transfersheet having an effective protection against surface smudging either dueto mechanical abrasive action or to moisture, or both, and which is aneffective bar to migration of oils from the transfer layer to anadjacent oil-absorptive sheet, but which is at the same time soconstructed that the character of the coloring matter deposited as animage in response to pressure is not impaired.

Variations and modifications may be made within the scope of thisinvention and portions of the improvements may be used without others.

I claim:

1. A pressure sensitive hectograph transfer element comprising afoundation sheet; a pressure or impact transferable dye-carrying coatingthereon; an intermediate protective layer composed essentially of waxsuperposed and adhered on said coating at a well-defined interface; anda surface protective layer of waxy material superposed on saidintermediate layer, the combined thickness of said layers beingapproximately .0002 inch, said transfer coating, intermediate andsurface layers being adhesively attached to their respective contactingsurfaces to form a composite layer and being frangible under inscribingpressure or impact to separate in image form from the foundation andsurrounding composite layer and transfer to a copy medium, and saidsurface layer forming the adhesive to bond the image to the copy medium.

2. A pressure sensitive hectograph transfer element comprising afoundation sheet; a wax-base dye-carrying transfer coating thereon; anintermediate layer composed primarily of waxy material and including ashielding component of lamelliform particles superposed on said transfercoating; and a surface protective layer comprising essentially waxymaterial superposed on said intermediate layer, said transfer coating,intermediate layer and surface layer being adhesively attached to theirrespective contacting surfaces to form a composite layer and beingfrangible under inscribing pressure or impact to separate in image formfrom the foundation and surrounding composite layer and transfer to acopy medium, and said surface layer forming the adhesive to bond theimage to the copy medium.

References Cited in the file of this patent UNITED STATES PATENTS1,546,747 Pembroke July 21, 1925 1,864,097 Sherman June 21, 19321,865,708 Sherman July 5, 1932 1,911,592 Supligeau et a1 May 30, 19332,069,648 Denner Feb. 2, 1937 2,072,943 Cohoe Mar. 9, 1937 2,118,888Lewis May 31, 1938 2,188,590 Bjorksten Jan. 30, 1940 2,213,645 AntrimSept. 3, 1940 2,279,604 Walti Apr. 14, 1942 2,322,367 Kjellstrand June22, 1943 2,342,643 Cessna Feb. 29, 1944 2,348,128 Groak May 2, 19442,355,225 MacWilliam Aug. 8, 1944 2,501,495 Carroll et a1 Mar. 21, 19502,554,909 Holik May 29, 1951 2,671,734 Rosenblum Mar. 9, 1954 FOREIGNPATENTS 856,878 France Aug. 13, 1940

1. A PRESSURE SENSITIVE HECTOGRAPH TRANSFER ELEMENT COMPRISING AFOUNDATION SHEET; A PRESSURE OR IMPACT TRANSFERABLE DYE-CARRYING COATINGTHEREON; AN INTERMEDIATE PROTECTIVE LAVER COMPOSED ESSENTIALLY OF WAXSUPERPOSED AND ADHERED ON SAID COATING AT A WELL-DEFINED INTERFACE; ANDA SURFACE PROTECTIVE LAYER OF WAXY MATERIAL SUPERPOSED ON SAIDINTERMEDIATE LAYER, THE COMBINED THICKNESS OF SAID LAYERS BEINGAPPROXIMATELY .0002 INCH, SAID TRANSFER COATING, INTERMEDIATE ANDSURFACE LAYERS BEING ADHESIVELY ATTACHED TO THEIR RESPECTIVE CONTACTINGSURFACES TO FORM A COMPOSITE LAYER AND BEING FRANGIBLE UNDER INSCRIBINGPRESSURE OR IMPACT TO SEPARATE IN IMAGE FORM FROM THE FOUNDATION ANDSURROUNDING COMPOSITE LAYER AND TRANSFER TO A COPY MEDIUM, AND SAIDSURFACE LAYER FORMING THE ADHESIVE TO BOND THE IMAGE TO THE COPY MEDIUM.